Testing the blast wave model with Swift GRBs

Authors: Curran, P. A.; Starling, R. L. C.¹; van der Horst, A. J.²; Wijers, R. A. M. J.³

Source: Monthly Notices of the Royal Astronomical Society, Volume 395, Number 1, May 2009 , pp. 580-592(13)

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Abstract:

The complex structure of the light curves of Swift Gamma-Ray Bursts (GRBs) has made the identification of breaks, and the interpretation of the blast wave caused by the burst, more difficult than in the pre-Swift era. We aim to identify breaks, which are possibly hidden, and to constrain the blast wave parameters; electron energy distribution, p, density profile of the circumburst medium, k, and the continued energy injection index, q. We do so by comparing the observed multiwavelength light curves and X-ray spectra of our sample to the predictions of the blast wave model. We can successfully interpret all of the bursts in our sample of 10, except two, within this framework and we can estimate, with confidence, the electron energy distribution index for 6 of the sample. Furthermore, we identify jet breaks in a number of the bursts. A statistical analysis of the distribution of p reveals that, even in the most conservative case of least scatter, the values are not consistent with a single, universal value. The values of k suggest that the circumburst density profiles are not drawn from only one of the constant density or wind-like media populations.

Keywords: radiation mechanisms: non-thermal; gamma rays: bursts; X-rays: bursts

Document Type: Research article

DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.14578.x

Affiliations: 1: Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH 2: NASA Postdoctoral Program Fellow, NSSTC, 320 Sparkman Drive, Huntsville, AL 35805, USA 3: Astronomical Institute, University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, the Netherlands

Publication date: 2009-05-01